IntelliJ IDEA 2016.3 Help

Using Local History

This section describes how to use
Local History, which is
your personal real-time version control system. Local History
is independent of external version control systems and works with the directories of your project
even when they are not under any VCS control.

Local history is cleared when you install a new version of IntelliJ IDEA or when you
invalidate caches.
Therefore, check in the changes to your version control system before performing these operations.